void main() {
  String str = '😊';
  print(str);
  print(str.length); // UTF-16
  print(str.runes.length); // UTF-32

  // runes 可以将utf-32 字符集表示的内容转成符号
  Runes input = new Runes('\u{1f680}');
  print(new String.fromCharCodes(input));

  // symbol
  Symbol a = #abc;
  print(a);

  Symbol b = new Symbol('abc');
  print(b);

  print(a == b);

  print(#abc == new Symbol('abc'));

  // 动态类型的变量
  dynamic foo = 'bar';
  foo = 1234;
  print(foo);
}
